void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    
    // Normalized pixel coordinates (from 0 to 1)
    vec2 uv = fragCoord/iResolution.xy;
    fragColor = vec4(uv, 0, 1.0);
    return;
    // Time varying pixel color
    vec3 col = 0.5 + 0.5*cos(iTime+uv.xyx+vec3(0,2,4));

    // Output to screen
    fragColor = vec4(col, 1.0);
}
